This invention relates to 2-substituted pyrido[2,3-d]-, pyrido[3,4-d]- and pyrido [4,3-d]pyrimidin-4(3H)-one and their use as herbicidal agents, and to processes for the preparation of 2-aminonicotinonitriles, useful as intermediates in the synthesis of the subject compounds.
Weeds, which can be broadly defined as any undesirable plants, cause considerable economic losses annually and are also objectionable for aesthetic reasons. Considerable effort is expended annually for removing and controlling the growth of weeds along highways, railway beds and in parks and gardens. Of most concern, however, is their interference with the growth of agricultural crops, thereby increasing the cost of producing these crops. Weeds are generally eliminated mechanically, such as by actual physical removal from the ground or by means of chemicals. Initially, the chemicals used for weed control were inorganic compounds, in particular the chlorates, chlorides and arsenites. These compounds are usually non-selective herbicides and kill all living plants. In the 1940's, attention was directed to more selective herbicides which would only destroy undesirable plants and cause little damage to agricultural crops. Most of these new herbicides were organic compounds and the first one developed, 2,4-D (2,4-dichlorophenoxyacetic acid) and its derivatives, is still widely used today for weed control.
In the interest of economy and selectivity, many other prototype organic structures have been examined for herbicidal activity. A limited series of quinazolines including 4-ethylamino-, 4-diethylamino-, 2-chloro-4-ethylamino- and 2-chloro-4-diethylaminoquinazoline are claimed as plant-growth regulators, British Pat. No. 822,069. In 1964-65, Deysson, et al., Compt. Rend., 259 (2), 479 (1964), Ann. Pharm. Franc., 23, 163, 229 (1965) reported the antimitotic properties of 1-methyl-1,4-dihydro-, 1-propyl-1,4-dihydro-, 3-methyl-3,4-dihydro-, 3-ethyl-3,4-dihydro-, 3-propyl-3,4-dihydro-, and 3-isopropyl-3,4-dihydro-4-quinazolines. U.S. Pat. No. 3,244,503 discloses a series of 3-alkyl and cycloalkyl substituted 2,4(1H,3H)-quinazolinediones, useful as herbicides.
The synthesis of 2-mercaptopyrido[2,3-d]pyrimidin-4(3H)-one derivatives, as diuretic and saluretic agents, is reported in British Pat. No. 1,272,060 and West German patent application No. 2,036,063, and the corresponding 2-hydroxypyrido[2,3-d]pyrimidin-4(3H)-ones in French Pat. No. 2,085,750, also claimed as diuretic agents.
Antiphlogistic and antipyretic activity is claimed for 2,3-disubstituted derivatives of pyrido[2,3-d]pyrimidin-4(3H)-ones on East German patent 49,610, while herbicidal and plant growth regulatory activity is claimed for 1,3-disubstituted pyrido[3,2-d]pyrimidin-2,4(1H,3H)-diones, West German patent application No. 1,932,160.
Ried, et al., Justus Liebigs Ann. Chem., 707, 250 (1967), have reported the preparation of 2-methylpyrido[3,4-d]pyrimidin-4(3H)-one and Dornow, et al., Chem. Ber., 98, 1505 (1965), the synthesis of a series of pyrido[2,3-d]pyrimidin-4(3H)-ones; neither study disclosed a utility for the prepared compounds.